This relates generally to electronic devices, and more particularly, to controlling components such as displays in electronic devices to enhance display longevity.
Electronic devices often include displays. Displays such as organic light-emitting diode (OLED) displays contain pixels that produce illumination without using a separate backlight unit. Other displays such as liquid crystal displays have backlight units. Light sources such as fluorescent lamps and light-emitting diodes can be used to generate backlight in a backlight unit.
Heat may be produced by the operation of the light-emitting diodes and other components in an electronic device such as processing circuitry, camera flash units, communications circuits such as circuits involved in communicating with external equipment, video circuits, and other devices.
High-temperature operation can degrade the performance of displays. Light-emitting diode light output typically decreases over time. Light-emitting diode lifetimes are sometimes measured in terms of lumen (light output) depreciation. When light-emitting diodes are simultaneously operated at elevated drive power levels and elevated temperatures, lumen depreciation can be accelerated (i.e., light-emitting diode lifetimes may be shortened). In displays with light-emitting diode backlights, operation at elevated temperatures may therefore result in accelerated decreases in backlight brightness. Displays with fluorescent lamp backlighting can also be degraded when operated at elevated temperatures due to accelerated reductions in available mercury, poisoning of the cathode, and phosphor degradation. In organic light-emitting displays, undesirable color shifts can develop as a display ages. These color shifts can be accelerated when organic light-emitting diodes are operated at elevated temperatures.
One possible way to ensure that displays perform satisfactorily over their desired lifetimes involves permanently restricting their operating power to conservatively low levels. By operating organic light-emitting diode pixels and display backlights at low brightness levels, display lifetimes can be extended to satisfactory levels, even in the presence of elevated temperatures.
However, imposing this type of limit on the brightness of a display may not be acceptable to a user of an electronic device, because it may become difficult or impossible to view images on a display in bright conditions.
It would therefore be desirable to be able to provide improved ways to control the operation of electronic devices with displays.